Ford Motorcraft 4-122 & 6-149 Diesel Starter

Fig. 7 Ford Motorcraft starting motor. 4-122 & 6-149 diesel engines (Typical):

DESCRIPTION
This type starting motor, Fig. 7, has the solenoid mounted on the starter housing. When the starter relay contacts are closed, the solenoid is energized and the starter drive is engaged to start the engine. During the engine starting, the starter is protected from excessive speed by an overrunning clutch in the drive. Current flows through the solenoid energizing coil until the solenoid plunger reaches the end of its travel, at which time the plunger closes a set of contacts that bypass the energizing coil. The holding coil keeps the starter drive engaged and passes current to the starting motor.

Fig. 4 Diagnosis chart:

DIAGNOSIS
When diagnosing this starter motor, refer to Fig. 4.

Fig. 8 Starter load test connections. Diesel starter:

IN-VEHICLE TESTING
Starter Load Test
1. Connect test equipment as shown in Fig. 8.
2. Ensure that no current is flowing through ammeter and heavy duty carbon pile rheostat portion of circuit.
3. Crank engine with ignition off and determine exact reading on voltmeter. This test is accomplished by disconnecting push on connectors at starter relay and by connecting remote control starter switch from positive battery terminal to S terminal on starter relay.
4. Stop cranking engine, then reduce resistance at carbon pile until voltmeter indicates the same reading as that obtained while starter cranked engine. Ammeter should read less than 375 amps.